1. Field of the Invention
The present invention relates to a conveyor apparatus for feeding a sheet material such as a sheet of glass, and more particularly to a conveyor apparatus for horizontally feeding, at uniform speed, a sheet material such as sheet glass that has been heated in a heating furnace.
2. Description of the Relevant Art
There have been known conveyor apparatus for horizontally feeding sheet glass at uniform speed in a heating furnace.
One typical sheet glass conveyor comprises an array of feed rolls having their axes extending perpendicularly to the direction in which the sheet glass is fed. The feed rolls have upper ends that jointly serve as a horizontal feed plane in which the glass is fed.
The feed rolls may be rotated at uniform speed by different mechanisms. According to one mechanism, gears are attached to respective ends of the feed rolls, and a chain driven by a motor and a train of gears are operatively coupled to the gears on the feed rolls for rotating the feed rolls. Another mechanism comprises a chain or an endless belt driven by a motor, with the feed rolls placed on the chain or the endless belt.
The former rotating mechanism is disadvantageous in that when the sheet glass is to be fed at a different speed, there is developed a backlash between the gears or the gears and the chain, causing the sheet glass to slip against the feed rolls. As a result, the sheet glass which has been softened with heat tends to be scratched or damaged by the feed rolls. The latter rotating mechanism is free of the backlash problem. However, it is tedious and time-consuming to locate any defective or damaged feed roll among the many feed rolls employed, and the sheet glass being fed is still liable to be scratched or damaged by a damaged feed roll.
A sheet glass conveyor that has been proposed to solve the aforesaid problems of the conventional sheet glass conveyor apparatus is disclosed in Japanese laid-open patent publication No. 3-16928.
The disclosed sheet glass conveyor comprises an array of feed rolls whose ends are placed on an endless belt. The feed rolls are individually shiftable between upper and lower positions by respective support rollers.
The proposed sheet glass conveyor does not suffer the backlash problem, and allows damaged rolls to be located and replaced easily. However, the feed rolls may not be rotated at different speeds because of the slippage developed between the feed rolls and the endless belt, with the result that the sheet glass that has been softened with heat is apt to be scratched.